1. Field of the Invention
This invention relates in general to communication systems, and more particularly, to a method and apparatus for providing adaptive equalization using non-linear digital filters.
2. Description of Related Art
One signal processing technique that is typically used in digital communication systems is channel equalization. The primary goal of equalization is to enhance the performance of a communication system in the presence of channel noise, channel distortion, multipath and multi-user interferences. Applications of channel equalization can be found in the consumer electronics, for example, in digital TV and personal communication systems, where various equalizers are used to increase the signal-to-noise ratio of an incoming signal and/or to reduce the bit error rate of the incoming signal.
Conventional equalization techniques generally rely on the use of linear filters. However, communications channels typically exhibit nonlinear characteristics that result from the existence of impulse noise and nonlinear distortion. In the presence of such nonlinearities, equalizers based on the linear filter theory perform poorly. This subsequently results in reduced system performance.
Accordingly, there is a need in the technology for a method and apparatus for providing adaptive equalization in a communication system, which overcomes a number of the aforementioned problems. There is also a need in the technology for providing adaptive equalization using non-linear filters, that provide robust frequency tracking and are resistant to interference during communications.
The present invention is a method and apparatus for equalizing a signal in a communication system. The signal is represented by samples at a time instant, and the samples are filtered using a sign permutation filter. An estimate of the signal is determined by a linear combination of the samples with corresponding weights. The error of the estimate is then computed. The weights are updated by an updating circuit to minimize the error.